Function calling is the bridge between language models and the real world. Learn how Claude, GPT-4, and other modern LLMs use structured function calls to interact with external APIs, databases, and services. This tutorial walks you through the fundamentals of function calling, from basic concepts to building a fully functional chatbot that retrieves weather data, executes database queries, and integrates with REST APIs. You'll start by understanding how function calling works under the hood, then progress to implementing practical examples using popular LLM platforms. By the end, you'll have built a multi-tool chatbot that can autonomously decide which functions to call based on user requests, handle API responses gracefully, and chain multiple function calls together to solve complex problems. Perfect for developers looking to move beyond simple text generation and build AI applications that actually do things.

Lessons

  1. Introduction to Function Calling — Understand how LLMs use functions to interact with external systems and why it matters (+50 XP)
  2. Designing Function Schemas — Learn to define clear, structured function schemas that LLMs can understand and use effectively (+75 XP)
  3. Function Calling with Claude — Implement your first function calls using Anthropic's Claude API and tool use framework (+100 XP)
  4. Building a Weather Chatbot — Create a practical chatbot that retrieves real weather data using function calling (+125 XP)
  5. Database Query Execution — Enable your LLM to safely query databases and return structured data from function calls (+125 XP)
  6. Chaining Functions and Complex Workflows — Master advanced patterns like function chaining and multi-step reasoning with tool use (+150 XP)
  7. Error Handling and Production Deployment — Deploy robust, production-ready function-calling applications with proper error handling (+150 XP)